Objective: Evaluate the association between carbon dioxide (pCO 2 ), cerebral blood flow (CBF), and cerebral autoregulation (CA) in preterm infants.
Study Design: Cerebral saturations (rScO 2, surrogate for CBF using NIRS) and mean arterial blood pressure (MAP) monitored for 96 h in infants <29 weeks gestation. Relationship between rScO 2 , the rScO 2 -MAP correlation (CA analysis) and pCO 2 category assessed by mixed effects modeling.
Results: Median pCO 2 differed by postnatal day (p < 0.0001)-pCO 2 increased between day 1 and 2, and low variability seen on day 4. A 5% increase in rScO 2 was noted when pCO 2 was >55 mmHg on each postnatal day (p < 0.001). No association observed between the overall rScO 2 -MAP correlation and pCO 2 . On day 1 only, the correlation coefficient decreased from 0.26 to -0.09 as pCO 2 category increased (p = 0.02).
Conclusions: CBF increased above a pCO 2 threshold of 55 mmHg, but overall, no association between pCO 2 and CA was noted.